Receiver circuits are used for both terrestrial and cable reception within televisions, digital video recorders, video cassette records, set-top box devices (such as cable and satellite tuners), frequency modulation (FM) radios, models, and other electronic devices. Some smart phones also utilize receiver circuits for television reception. In general, receiver circuits include a tuner that selects a narrowband signal from within a wide or broad-band signal having multiple channels. The tuner includes bandpass filters, amplifiers, and mixer circuits for selecting a desired channel and for rejecting unwanted channels, noise and interference.
Reception of terrestrial broadcast signals typically needs a very good noise figure, in part, because the terrestrial broadcast signals tend to have large signal power differences from channel to channel. The noise figure (NF) is a measure of degradation of the signal-to-noise ratio (SNR), caused by components in a radio frequency (RF) signal chain. In contrast, cable signal reception typically needs a good return loss to avoid attenuation in the received signal, since, in cable broadcasts, the power tends to be relatively even and well-controlled across the channels. Return loss (RL) or reflection loss is the loss of signal power resulting from the reflection caused at a discontinuity in a transmission line or optical fiber. This discontinuity can be a mismatch with the terminating load or with a device inserted in the transmission line. Unfortunately, there is a tradeoff between the noise figure and the return loss, in part, because impedance matching circuitry that can be used to provide a good return loss can adversely impact the noise figure, and vice versa.